Implantable medical devices that utilize electromechanical actuators may be used for applications such as blood pumps, mechanically actuated valves, or artificial muscle. Electric motors (Jarvik, Intraventricular Artificial Hearts and Methods of Their Surgical Implantation and Use, U.S. Pat. No. 4,994,078), solenoids (Peters, Heart Assist Devices, Systems and Methods, U.S. Pat. No. 7,357,771) or linear actuators (Goldowski, Linear Pump, U.S. Pat. No. 5,924,975) that are used to power these devices utilize metals such as copper or iron, which are very susceptible to corrosion if exposed to body fluids. Encapsulation, coating, potting, and similar methods that cover the metals with polymer barrier layers may be used for short term implantation in the body, such as days or weeks. But for electromechanical devices that must function for many years, complete exclusion of body fluids by use of hermetically sealed enclosures is required. For decades pacemakers have utilized welded titanium cases to isolate batteries and electronics components, and have brought electrical conductors through the walls of these cases using hermetic feedthroughs having metal to ceramic seals. Examples include Kraska, Hermetic Electrical Feedthrough Assembly, U.S. Pat. No. 4,678,868, and Sawchuk, Protective Feedthrough, U.S. Pat. No. 5,759,197. Many feedthroughs for heart devices and others electronic implants such as cochlear implants or neuro-stimulators have been disclosed in the prior art including designs with multiple contacts such as Taylor, Implantable Medical Device with Multi-Pin Feedthrough, U.S. Pat. No. 5,866,851, or Kuzma, Cochlear Prosthesis Package Connector, U.S. Pat. No. 4,516,820. This has been accomplished using materials such as titanium supports, aluminum oxide insulators, platinium-irridium conductors and pure gold brazing to form a seal between the conductors and the insulators, and between the insulators and the titanium support or other methods such as glass to metal feedthroughs, (Spillman, Glass to Metal Seal, U.S. Pat. No. 6,670,074)
All of these feedthroughs are relatively small components, but in most applications the smallest and most compact geometries are not essential. For example, Wampler shows a multi-pin feedthrough in U.S Patent Application No. 20070231135, entitled Rotary Blood Pump. This device uses three individual feedthroughs located in a recess of a wall of the housing, and is placed in a portion of the centrifugal pump housing near the diffuser, where there is adequate space to weld a ferrule to the housing. LaRose, in U.S. Patent Application No. 20070100196, discloses a very small axial flow blood pump, in which hermetic feedthroughs may be used for the electrical leads, but does not disclose a compact arrangement for the feedthroughs. Rather, LaRose states that the hermetically sealed motor stator enclosure may be welded to a tubular pump housing that passes through it, without providing a structure to compactly provide feedthroughs for the electrical leads. But with very small diameter, generally cylindrical actuators, such as tiny axial blood pumps disclosed by Siess in U.S. Patent Application No. 20040046466, entitled Miniature Motor, or by Jarvik in U.S. Patent Application No. 20060195004, entitled, Minimally Invasive Transvalvular Ventricular Assist Device, the available space to provide power leads may be as little as 2 mm or less. In Siess, no hermetic feedthrough is provided because the device is for short-term application. The present invention provides an extremely compact hermetically sealed feedthrough for tiny electromechanical actuators that integrate the feedthrough structure with the device structure, without the use of a ferrule or the need for welding the feedthrough onto an enclosure containing the stationary motor or solenoid coils.